Perovskite-type metal oxide compounds and methods of making and using thereof

ABSTRACT

Perovskite-type catalyst consists essentially of a metal oxide composition is provided. The metal oxide composition is represented by the general formula A a-x B x MO b , in which A is a mixture of elements originally in the form of single phase mixed lanthanides collected from bastnasite; B is a divalent or monovalent cation; M is at least one element selected from the group consisting of elements of an atomic number of from 23 to 30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3 when a is 1 or b is 4 when a is 2; and x is a number defined by 0≦x&lt;0.5. Methods of making and using the perovskite-type catalysts are also provided. The perovskite-type catalyst may be used to make a catalytic converter. Methods of making a catalytic converter are also provided.

RELATED APPLICATION

[0001] This application is a continuation-in-part of application Ser.No. 08/797,578, filed on Feb. 7, 1997, which in turn is acontinuation-in-part of application Ser. No. 08/630,603, filed on Apr.10, 1996, which applications are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to perovskite-typecatalysts which are useful in carbon monoxide oxidation, hydrocarbonoxidation, nitrogen oxide reduction and oxidation of trapped sootparticles. In addition, the present invention relates to perovskite-typematerials displaying so-called giant magnetoresistance (GMR).Furthermore, the present invention relates to methods of making andusing perovskite-type catalysts and materials.

[0004] 2. Description of Related Art

[0005] Perovskite compositions are nominally designated as ABO₃, inwhich A represents a rare earth metal, such as lanthanum, neodymium,cerium or the like, and B represents a transition metal such as cobalt,iron, nickel or the like. It is known in the art that perovskite-typematerials are useful for the catalytic oxidation and reduction reactionsassociated with the control of automotive exhaust emissions. It is alsoknown that perovskite materials (powders, single crystals and thinfilms) containing Mn on the B-site show giant magnetoresistance effect(GMR), such that on application of a magnetic field, the electricalresistivity of the material drops drastically due to a field-inducedswitching of the crystal structure. For this reason, GMR has attractedconsiderable attention for device applications, such as magneticrecording heads.

[0006] Several techniques have been used to produce perovskite-typecatalyst materials for the treatment of exhaust gases from internalcombustion engines. The ability of such materials to effectively treatinternal combustion exhaust gases depends on the three-way activity ofthe material, i.e., the capability for nitrogen oxide reduction, carbonmonoxide oxidation and unsaturated and saturated hydrocarbon oxidation.The following patents describe such materials and techniques in thethree-way catalytic application: U.S. Pat. Nos. 3,865,752; 3,865,923;3,884,837; 3,897,367; 3,929,670; 4,001,371; 4,049,583, 4,107,163;4,126,580; 5,318.937. In particular, Remeika in 3,865,752 describes theuse of perovskite phases incorporating Cr or Mn on the B-site of thestructure showing high catalytic activity. Lauder teaches in 4,049,583(and 3,897,367) the formation of single-phase perovskite materialsshowing good activity for CO oxidation and NO reduction. Tabata in4,748,143 teaches the production of single-phase perovskite oxidationcatalysts where the surface atomic ratio of the mixed rare earthelements and the transition metal is in the range of 1.0:1.0 to 1.1:1.0.The rare-earth component can be introduced using a mixed rare-earthsource called “Lex 70” which has a very low Ce content. Tabata furtherteaches in 5,185,311 the support of Pd/Fe by perovskites, together withbulk ceria and alumina, as an oxidation catalyst. The perovskite iscomprised of rare earths on the A-site and transition metals on theB-site in the ratio 1:1.

[0007] In addition to these patents there are numerous studies reportedin the scientific literature relating to the fabrication and applicationof perovskite-type oxide materials in the treatment of internalcombustion exhaust emissions. These references include Marcilly et al.,J. Am. Ceram. Soc., 53 (1970) 56; Tseung et al., J. Mater. Sci., 5(1970) 604; Libby, Science, 171 (1971) 449, Voorhoeve et al., Science,177 (1972) 353; Voorhoeve et al., Science, 180 (1973); Johnson et al.,Thermochimica Acta, 7 (1973) 303; Voorhoeve et al., Mat. Res. Bull., 9(1974) 655; Johnson et al., Ceramic Bulletin, 55 (1976) 520; Voorhoeveet al., Science, 195 (1977) 827; Baythoun et al. J. Mat. Sci., 17 (1982)2757; Chakraborty et al., J. Mat. Res., 9 (1994) 986. Much of thisliterature and the patent literature frequently mention that the A-siteof the perovskite compound can be occupied by any one of a number oflanthanide elements (e.g., Sakaguchi et al., Electrochimica Acta, 35(1990) 65). In all these cases, the preparation of the final compoundutilizes a single lanthanide, e.g., La₂O₃. Meadowcroft, in Nature, 226(1970) 847, refers to the possibility of using a mixed lanthanide sourcefor the preparation of a low-cost perovskite material for use in anoxygen evolution/reduction electrode. U.S. Pat. No. 4,748,143 refers tothe use of an ore containing a plurality of rare-earth elements in theform of oxides for making oxidation catalysts.

[0008] In addition to the above-mentioned techniques, other techniqueshave been developed for the production of perovskite materialscontaining Mn on the B-site which show giant magnetoresistance effect(GMR). Such materials are generally made in the forms of powders, singlecrystals and thin films. A common technique is the growth ofsingle-crystal from a phase-pure perovskite source (see, for example,Asamitsu in Nature, 373 (1995) 407). All such techniques use aphase-pure perovskite compound with a single lanthanide on the A-site,in addition to an alkaline earth dopant. An example of such phase-pureperovskite compounds is La_(1-x)Sr_(x)Mno₃.

[0009] It is also known in the art that it is difficult and expensive toprepare individual rare-earth compounds such as individual lanthanides.The cost is high for making perovskite-type materials with a singlelanthanide on the A-site. Therefore, a need exists for using low-coststarting materials to manufacture inexpensive catalyst materials,simultaneously having high temperature stability and high three-wayactivity for use in conversion of CO, hydrocarbons and oxides ofnitrogen in modem gasoline-powered automobiles. A need also exists forthe manufacture of bulk materials, thin films and single-crystals ofmaterials showing GMR, using inexpensive starting materials.

SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide improvedcatalyst materials with three-way activity, manufactured frominexpensive starting components. It is also an object of the presentinvention to provide a perovskite-type metal oxide compound having giantmagnetoresistance effect. It is further an object of the presentinvention to provide a method of making and using improved catalystmaterials and the perovskite-type metal oxide compounds of the presentinvention.

[0011] Accordingly, one object of the present invention is to provide aperovskite-type catalyst consisting essentially of a metal oxidecomposition. The metal oxide composition is represented by the generalformula A_(a-x)B_(x)MO_(b), in which A is a mixture of elementsoriginally in the form of single phase mixed lanthanides collected frombastnasite; B is a divalent or monovalent cation; M is at least oneelement selected from the group consisting of elements of an atomicnumber of from 22 to 30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3when a is 1 or b is 4 when a is 2; and x is a number defined by 0≦x<0.7.

[0012] In a preferred embodiment, the single phase perovskite-typematerials of the present invention have a formula A_(1-x)B_(x)MO₃, andpreferably x is about 0 to 0.5.

[0013] In another preferred embodiment, the single phase materials ofthe present invention are perovskite-type materials having a formulaA_(2-x)B_(x)MO₄.

[0014] Another object of the present invention is to provide aperovskite-type metal oxide compound represented by the general formulaA_(a-x)B_(x)MO_(b), in which A is a mixture of elements originally inthe form of single phase mixed lanthanides collected from bastnasite; Bis a divalent or monovalent cation; M is at least one element selectedfrom the group consisting of elements of an atomic number of from 22 to30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3 when a is 1 or b is 4when a is 2; and x is a number defined by 0≦x<0.7. The perovskite-typemetal oxide compound of the present invention contains Mn on its B-site.

[0015] The present invention also provides a catalytic converter. Thecatalytic converter comprises:

[0016] (a) a perovskite-type catalyst comprising a metal oxidecomposition represented by the general formula:

A_(1-x)B_(x)MO₃

[0017] wherein

[0018] A is a mixture of elements originally in the form of a singlephase mixed lanthanide collected from bastnasite;

[0019] B is a divalent or monovalent cation;

[0020] M is at least one element selected from the group consisting ofelements of an atomic number of from 22 to 30, 40 to 51, and 73 to 80;

[0021] x is a number defined by 0≦x<0.5; and

[0022] (b) a solid structure for supporting the catalyst.

[0023] In a preferred embodiment, the catalytic converter also comprisesa carrier powder. The peroviskite-type catalyst may be in a bulk form orin the form of a dispersion.

[0024] Another object of the present invention is to provide a method ofpreparing a perovskite-type catalyst consisting essentially of a metaloxide composition having component elements represented by the generalformula A_(a-x)B_(x)MO_(b), in which A is a mixture of elementsoriginally in the form of single phase mixed lanthanides collected frombastnasite; B is a divalent or monovalent cation; M is at least oneelement selected from the group consisting of elements of an atomicnumber of from 22 to 30, 40 to 51, and 73 to 80; a is 1 or 2; b is 3when a is 1 or b is 4 when a is 2; and x is a number defined by 0≦x<0.7.

[0025] The method comprises forming a homogeneous mixture of a singlephase mixed lanthanide salt collected from bastnasite and respectivesalts or oxides, of elements B and M and forming a perovskite-type metaloxide composition from said homogeneous mixture.

[0026] A further aspect of the present invention provides a method ofmaking a catalytic converter of the present invention. The methodcomprises:

[0027] (a) providing a perovskite-type catalyst comprising a metal oxidecomposition represented by the general formula:

A_(1-x)B_(x)MO₃

[0028] wherein

[0029] A is a mixture of elements originally in the form of a singlephase mixed lanthanide collected from bastnasite;

[0030] B is a divalent or monovalent cation;

[0031] M is at least one element selected from the group consisting ofelements of an atomic number of from 22 to 30, 40 to 51, and 73 to 80;

[0032] x is a number defined by 0≦x<0.5;

[0033] (b) providing a support structure having a surface;

[0034] (c) forming a stable slurry suspension of the perovskite-typecatalyst; and

[0035] (d) depositing the suspension of the perovskite-type catalyst onthe surface of the support.

[0036] In one embodiment of the present invention, the perovskite-typecatalyst may be in a bulk form or in the form of a dispersion. A carrierpowder may be mixed with the bulk perovskite-type catalyst to form theslurry suspension and then be deposited on the surface of the support.Alternatively, a carrier powder may be used to form a perovskite-typecatalyst in the form of a dispersion.

[0037] The present invention is further defined in the appended claimsand in the following description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above-mentioned and other features of the present inventionand the manner of obtaining them will become more apparent, and will bebest understood by reference to the following description, taken inconjunction with the accompanying drawings. These drawings depict atypical embodiment of the present invention and do not therefore limitits scope. They serve to add specificity and detail in which:

[0039]FIG. 1 shows a processing route of bastnasite and its mixedlanthanide derivatives.

[0040]FIG. 2 shows the X-ray diffraction trace of a perovskite materialof the present invention.

[0041]FIG. 3 shows the three-way catalytic activity of a perovskitematerial of the present invention.

[0042]FIG. 4 shows the three-way catalyst “light off” test.

[0043]FIG. 5 shows the three-way catalytic activity of theperovskite-based catalyst of composition Ln_(0.8)Sr₀ ₂Mn_(0.9)Ni₀₀₄Pd_(0.06)O₃ in an exhaust gas stream.

[0044]FIG. 6 shows the three-way catalytic activity of theperovskite-based catalyst of compositionLn_(1.4)Sr_(0.3)Mn_(0.9)Ni_(0.04)Ru_(0.06)O₃ in an exhaust gas stream.

DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention is based on the discovery that single phasemixed lanthanides collected from bastnasite can be used in makingperovskite-type materials. According to the present invention, singlephase mixed lanthanides from bastnasite can be used to makeperovskite-type catalysts with improved activities. The catalysts of thepresent invention have three-way activity and can be used for theremoval of unsaturated and saturated hydrocarbons, nitrogen oxides andcarbon monoxide from the exhaust gases of internal combustion enginesand from industrial waste gases. They also exhibit high thermal andchemical stability.

[0046] As discussed above, the source of the lanthanide component inprior art is an oxide, carbonate, nitrate or acetate of one lanthanideelement, with a high degree of purity with respect to other lanthanides,or a mixture of highly purified lanthanide elements. The perovskitematerials of the present invention overcome the disadvantage of usingrelatively expensive, research-grade sources for the lanthanideelements. The advantage of the use of a mixed lanthanide source relatesto the need for an inexpensive fabrication route. The cost of producingperovskites using single phase mixed lanthanides of the presentinvention is three to four times less expensive than the cost of using asingle rare-earth element.

[0047] Accordingly, the present invention provides a single phaseperovskite-type catalyst consisting essentially of a metal oxidecomposition represented by the general formula, A_(a-x)B_(x)MO_(b) inwhich A is a mixture of elements originally in the form of single phasemixed lanthanides collected from bastnasite; B is a divalent ormonovalent cation; M is at least one element selected from the groupconsisting of elements of an atomic number of from 22 to 30, 40 to 51,and 73 to 80; a is 1 or 2; b is 3 when a is 1 or b is 4 when a is 2; andx is a number defined by 0≦x<0.7. In a preferred embodiment, the singlephase perovskite materials of the present invention have a formulaA_(1-x)B_(x)MO₃, and preferably x is about 0 to 0.5. In anotherpreferred embodiment, the single phase materials of the presentinvention are perovskite-type materials having a formulaA_(2-x)B_(x)MO₄. In a further preferred embodiment, the single phaseperovskite materials of the present invention have the general formulaA_(a-x)B_(x)MO_(b). in which A is a mixture of elements selected fromthe group consisting of lanthanides of an atomic number of from 57 to 71or, alternatively, A is a mixture of elements selected from the groupconsisting of yttrium and lanthanides of an atomic number of from 57 to71.

[0048] A single phase mixed lanthanide is a single compound wherein thecation positions in the compound's crystal structure can be occupied bya variety of lanthanides. Alternatively, the cation positions of thesingle phase mixed lanthanide may be occupied by a variety oflanthanides. The single phase mixed lanthanides of the present inventionare generated from bastnasite ore. They may contain a number oflanthanide cations and nitrate, carbonate or chloride anions. Thesemonophasic materials may be hydrated materials, namely, they may containwaters of hydration. Thus, hydroxyl ions may take up anion positions inthe lattice of the monophasic material.

[0049] It is known in the art that bastnasite is an ore of a mixedlanthanide fluoride carbonate. The mixed lanthanide fluoride carbonatesof bastnasite adopt a crystal structure with discrete layers of [LnF]and [CO₃] (Y. Ni et al., Am. Mineral., 78 (1993)415), wherein F can bereplaced by OH (M. Fleischer, Can. Mineral, 16 (1978) 361).

[0050] Different lanthanide (Ln) derivatives can be prepared frombastnasite through methods commonly known in the art. Examples of suchmethods are described in Cer. Eng. Sc. Proc. by B. T. Kilbourn, 6 (1985)pp. 1331-1341, and in The Discovery and Industrialization of the RareEarths by Fathi Habashi, UNOCAL 76 MOLYCORP (1994), FIG. 14, the text ofwhich is incorporated herein by reference. A typical flow chart relatingLn derivatives obtained from bastnasite ores is shown in FIG. 1.According to FIG. 1, bastnasite ore is first treated by comminution andfloatation to generate bastnasite concentrate. Through acid dissolutiontechniques, Ln carbonate, Ln chloride or Ln nitrate is generated fromthe bastnasite concentrate. Through roast and acid leaching techniques,soluble and insoluble fractions are generated from the bastnasiteconcentrate. La concentrate is from the soluble fraction, and Ceconcentrate is from the insoluble fraction. Further solution extractionfrom the Ln concentrate produces low-Ce (i.e., 4% CeO, when analyzed onan Ln oxide basis) and mixed Ln compounds.

[0051] Ln derivatives can be classified in terms of steps needed toproduce them. Both the bastnasite concentrate and the Ln derivativesgenerated by acid dissolution contain a natural ratio of Ln's. A naturalratio of Ln's is a ratio identical or close to their naturaldistribution proportions in bastnasite ores. A typical analysis on a Lnoxide basis is: 4.0% Pr oxide, 50.5% Ce oxide, 33.7% La oxide, and 11.8%Nd oxide. It is understood that this ratio may vary owing to inherentvariability, not only in the ore body but also in the mineral itself.Both the La and Ce concentrates contain a modified ratio of Ln's. Amodified ratio of Ln's is a ratio different from the natural ratio ofLn's, and a ratio existing in any by-products of the processing route ofbastnasite is shown in FIG. 1.

[0052] The single phase mixed lanthanides used in the present inventionmay be generated from any of the above-mentioned concentrates. They mayhave a natural ratio of Ln's or a modified ratio of Ln's. In general,any single phase mixed lanthanides generated from any of theabove-mentioned concentrates may be used as a lanthanide source formaking a perovskite-type material of the present invention.

[0053] For example, Ln derivatives generated from bastnasite concentrateby acid dissolutions, such as, but not limited to, Ln chloride, Lncarbonate and Ln nitrate, are single phase pure compounds with a mixtureof Ln cations, and can be used as an Ln source for the purpose of thepresent invention. Such Ln derivatives have a natural ratio of Ln's andare cerium-rich. Likewise, single phase mixed lanthanides, such as, butnot limited to, hydrated mixed lanthanide carbonate or hydrated mixedlanthanide nitrate, may be crystallized as single phase compounds with amixture of Ln cations coming out of a solution of La concentrate. Suchsingle phase mixed lanthanides have a modified ratio of Ln's. Forexample, they may contain about 4% of CeO₂ when analyzed on an Ln oxidebasis.

[0054] The perovskite-type materials of the present invention are dopedon the A-site with sufficient and appropriate monovalent or divalentcations to form electrically conductive, monophasic perovskites withhigh catalytic activity. The examples of monovalent or divalent cationsinclude, but are not limited to, Na, K, Li, Ca, Sr, Ba, Pb and the like.The amount of monovalent or divalent cations are sufficient andappropriate if they are in such an amount that the bulk composition'satomic ratio of element M in the B site and the A and B elements in theA site are about 1:1.

[0055] Similarly, a sufficient and appropriate M element is used for theB site of the perovskite or perovskite type materials of the presentinvention. M is one or more elements with atomic numbers lying in therange 22 to 30, 40 to 51, and 73 to 80. Examples of M element include,but are not limited to, Fe, Mn, Co, Ni, Ru, Cr, Pd, Cu and the like. Theamount of M elements is sufficient and appropriate if they are in suchan amount that the bulk composition's atomic ratio of element M in the Bsite and the A and B elements in the A site are in 1:1. In a preferredembodiment, the Mn element is in B-site.

[0056] The present invention also provides a method of making theperovskite-type materials of the present invention. The method comprisesthe steps of making a homogeneous mixture of single phase mixedlanthanide salts collected from bastnasite and respective salts, oroxides, of elements B and M, and forming the perovskite-type metal oxidecomposition from the homogeneous mixture.

[0057] The homogenous mixture of salts may be in a form of a solution ora form of a solid. The homogenous mixture may be formed by dissolving asingle phase lanthanide salt, together with salts containing elements Band M, respectively, in a solution such as water and also can be formedby dissolving in acid, e.g., vitric acid. The mixture may also be formedby grinding a single phase lanthanide salt with salts or oxides ofelements B and M. Other methods known in the art for forming thehomogenous mixture may also be used. The salts used in the method of thepresent invention may be nitrates, carbonates, hydroxides, acetates,oxalates or chlorides of component elements A, B and M. Oxides of B andM may also be used to make the homogenous mixture. The amount of eachsalt used is a function of the desired composition in the finalperovskite compound.

[0058] A perovskite-type metal oxide material may be formed from themixture by techniques such as, but not limited to, pelletizing,spray-drying, sintering or calcination. Those techniques may be usedalone or in combination to obtain perovskite-type metal oxide materials.

[0059] In a preferred embodiment, a malic acid solution technique isused when the homogenous mixture is in a form of a solution. Forexample, the following salts may be dissolved in a solution such aswater to form a homogenous mixture: a single phase lanthanide salt, suchas, but not limited, to single phase mixed hydrated lanthanidecarbonate, single phase mixed hydrated lanthanide nitrate or the like; asalt of elements B, such as, but not limited to, calcium nitratetetrahydrate, strontium nitrate or the like; and one or more salts ofelement M, such as, but not limited to, cobalt nitrate hexahydrate,hydrated manganese nitrate, hydrated chromium nitrate, hydrated ironnitrate, hydrated palladium nitrate, nickel nitrate or the like. Thenmalic acid may be added and dissolved into the solution. A foam-likeprecipitate is formed through heating the solution to a temperaturebetween 190 and 310° C. in air. The foam can be heated or calcined to atemperature of 400° C. or higher to form the perovskite-type material.In a preferred embodiment, the form is calcined in a temperature at arange of 500-1100° C. in air for about 1-25 hours. Periodic grindingduring the calcining process is preferred. Alternatively, when anadditional and different element M is desired, the salt or oxide form ofsuch an element may be added to the precipitate and powdered or sinteredtogether with the precipitate to form a powder of single phaseperovskite-type metal oxide materials having multiple M elements.

[0060] In another preferred embodiment, a sintering or calciningtechnique is used when the homogenous mixture is in a form of a solid.For example, a single phase mixed lanthanide salt may be mixed withoxides of elements B and M by grinding and homogenizing to form ahomogenous mixture. Then the mixture can be powdered or sintered attemperatures from 700 to 1000° C. to form a powder of single phaseperovskite-type metal oxide materials.

[0061] The powders of perovskite-type materials can be further formedinto pellets or beads. Techniques such as uniaxial cold press and thelike may be used to form the pellets or beads.

[0062] The metal oxide materials made by the method of the presentinvention have perovskite structure and they are single phase materials.X-ray diffraction analysis is used to show the perovskite structure ofmaterials and the presence, if any, of second phases or impurity phases.The Brunauer, Emmett and Teller (B.E.T.) surface area is measured by agas absorption apparatus for proving how fine-grained the powder is. Thesurface area is measured and is normalized to the weight of solid, i.e.,m²/g. A high m²/g (specific surface area) corresponds to a smallfundamental grain or particle size. Catalytic functions occur onsurfaces; therefore, it is important that a catalyst can be made with alarge specific surface area.

[0063] The perovskite-type material of the present invention may be in abulk form or in the form of a dispersion, depending on the methods usedto make it. A perovskite-type material is in a bulk form if it is theonly material present in the system. On the other hand, aperovskite-type material is in the form of a dispersion if the systemcontains not only perovskite-type material, but also carrier materials.In this form, the perovskite-type material is made up of a large numberof small perovskite particles existing on the surfaces of carriermaterials (alumina, etc.).

[0064] A bulk perovskite-type material may be made by any methoddescribed above. The above-described methods may also be used to make aperovskite-type material in the form of a dispersion if the methodsfurther include a step of mixing or impregnating a solution of thehomogenous mixture with a carrier material. For example, in accordancewith one embodiment of the present invention, a perovskite-type catalystin the form of a dispersion may be made by the steps of: (a) forming asolution of a homogeneous mixture of single phase mixed lanthanide saltscollected from bastnasite and respective salts or oxides of elements Band M, (b) mixing or impregnating the solution with a carrier material,and (c) calcining the impregnated carrier material under a conditionthat allows perovskite-type metal oxide composition to be formed on thecarrier material.

[0065] For the purpose of the present invention, a carrier material maybe a porous solid oxide that is, itself, not catalytically active.Carrier materials are used to provide a high surface area for thedispersed phase, and one that is stable at high temperatures and in arange of reducing and oxidizing conditions. In one embodiment of thepresent invention, carrier material is used in a powder form. Examplesof a carrier material include, but are not limited to, inert powder suchas gamma-alumina, any ceria-based powders (imparting oxygen storagecapacity), or any mixture of titania, silica, alumina (transition andalpha-phase), ceria, zirconia, Ce_(1-x)Zr_(x)O₂, and all the possibledoped ceria formulations.

[0066] The single phase perovskite-type metal oxide materials of thepresent invention can be used as a catalyst. The perovskite-typecatalyst of the present invention may be used as is, or after beingdeposited on carriers of various types and forms. They may take the formof pellets and particles which may be of uniform composition. They maytake a supported form with the active ingredient being dispersed throughor present as a coating on the individual bodies.

[0067] For example, the perovskite-type material of the presentinvention can be extruded or molded into monolithic bodies, includinghoneycombs that consist of channels running the length of the body withthin interconnected walls. The methods of making such extrusions arewell known in the art. Briefly, in making the extrusions, organiccompounds and liquids are added to the perovskite-type powders such thata plastic mass of appropriate rheological properties is formed. Thisbody is extruded through an appropriately designed die to form a greenbody and is then heat-treated or calcined at temperatures to impart asufficient mechanical strength and durability and to completely removeall organic additions.

[0068] The perovskite-type powder of the present invention also may beformed into an open cell foam according to methods known in the art.Briefly, the ceramic powder which is to be formed into a foam is mixedwith carbon powder. The mixture is heated to high temperature in asufficiently oxygen-containing atmosphere such that the carbon supportis removed leaving a solid ceramic foam with open, interconnected cells.

[0069] In addition, the perovskite-type powder of the present inventionmay be deposited or applied to the surface of a ceramic honeycomb orsome other monolith. The ceramic honeycomb may be a type of alumina,mullite, cordierite or some other alumino-silicate support. Theapplication can occur via a washcoat, as known in the art.Alternatively, the perovskite-type materials of the present inventionmay also be deposited or applied to the surface of a metal honeycombsupport. Preferably, all the supports, either metallic or ceramic, offera three-dimensional support structure.

[0070] Furthermore, the perovskite-type powder of the present inventionmay be dispersed on the ceramic or metallic support by impregnating thesupport with the same solution used to make the perovskite-type powderin accordance with the present invention. Preferably, the support ispre-coated with carrier powders. The impregnated support is heated to ahigh enough temperature to allow the perovskite-type phase to form onthe surface of the carrier powders of the support in a highly dispersedstate.

[0071] One aspect of the present invention also provides a catalyticconverter and a method of making a catalytic converter. For the purposeof the present invention, the term “catalytic converter” refers to asolid structure having catalytic activity. The solid structure may beenclosed in a housing, i.e., a metal can. In general, the catalyticconverter comprises a structural support and a catalyst that coats thesupport. A catalytic converter contains the appropriate type and amountof catalyst so that it can fulfill a precise catalytic function. Forexample, it may perform a conversion function. The conversion can be ofgases into other gaseous products, liquids into other liquids, liquidsinto gaseous products, solids into liquids, solids into gaseousproducts, or any combination of these specific conversions. In allcases, the conversion reaction or reactions are deliberate andwell-defined in the context of a particular application, i.e.,simultaneous conversion of NOx, HC and CO, conversion of MTBE to carbondioxide plus steam, etc.

[0072] In accordance with one embodiment of the present invention, acatalytic converter of the present invention includes a perovskite-typecatalyst of the present invention and a structure for supporting thecatalyst. In one embodiment of the present invention, a catalyticconverter may also contain a carrier material. The perovskite-typecatalyst contained in the converter may be in a bulk form or in the formof a dispersion. The converter may also contain one or more differentcatalysts which are in the same form or different forms.

[0073] The converter may contain one carrier material or a mixture ofdifferent carrier materials. Preferably, the carrier materials are in apowder form. The carrier material may be an inert powder or any othercarrier materials that are known in the art for forming a washcoat on asupport. The term “washcoat” as used herein refers to a coating of oxidesolids that is formed onto a solid support structure. For the purpose ofthe present invention, the oxide solids may be carrier oxides or one ormore catalyst oxides or mixture of carrier oxides and catalyst oxides(i.e., perovskite-type materials). A washcoat may be formed by forming aslurry of the oxide solids and depositing, i.e., washing, the slurryonto the support structure. Other methods that are known in the art forforming a washcoat on a support are also included in the presentinvention. Examples of a carrier material include, but are not limitedto, inert powders such as gamma-alumina, any ceria-based powders(imparting oxygen storage capacity), or any mixture of titania, silica,alumina (transition and alpha-phase), ceria, zirconia, Ce_(1-x)Zr_(x)O₂,and all the possible doped ceria formulations.

[0074] For the purpose of the present invention, a structure forsupporting a catalyst of the present invention may be any supportstructures known in the art. In one embodiment of the present invention,the structure is a honeycomb support. The honeycomb support may be aceramic honeycomb support or a metal honeycomb support. In a differentembodiment, the support structure may be in a form of beads or pellets.

[0075] In accordance with another embodiment of the present invention, acatalytic converter of the present invention may also contain anon-perovskite type catalyst, in addition to the perovskite-typecatalyst, for achieving different conversion results. For example, thenon-perovskite-type catalyst may be a base, a noble metal or a mixturethereof. Examples of a base metal catalyst include, but are not limitedto, metallic elements with atomic numbers 3-4, 11-15, 19-32, 37-43,48-52, 56-75, 80-83. Examples of a noble metal catalyst include, but arenot limited to, elements with atomic numbers 44, 45, 46, 47, 76, 77, 78and 79.

[0076] Different methods may be used to make the catalytic converters ofthe present invention. For example, in one embodiment, perovskite-typecatalysts of the present invention in bulk form may be suspended to forma stable suspension and deposited to a solid support structure bymethods known in the art. Alternatively, the bulk catalyst may be mixedwith a carrier powder or pre-mixed carrier powders, i.e., inert powderssuch as gamma-alumina, any ceria-based powders or a mixture thereof, toform a stable slurry suspension. The slurry suspension is then depositedto a solid support by a slurry deposition technique that is known in theart.

[0077] In accordance with another embodiment of the present invention, acatalytic converter of the present invention is made by depositing theperovskite-type catalyst of the present invention in the form of adispersion onto a solid support. According to this embodiment, asolution of a homogenous mixture of salts of element A and respectivesalts or oxides of elements B and M may be mixed and impregnated into anumber of carrier powders including, but not limited to, titania,silica, alumina (transition and alpha-phase), ceria, zirconia,Ce_(1-x)Zr_(x)O₂ and all the possible doped ceria formulations. Theseimpregnated powders are dried and calcined at elevated temperatures toform perovskite-type catalysts in the form of a dispersion. The formedcatalysts may be then slurry deposited individually, in combinations, orsequentially onto commercially available support structures.Alternatively, the carrier powders may be pre-mixed, and the solutionsof the homogenous mixtures are impregnated into pre-mixed carrierpowders, such as ceria-alumina mixtures. For the purpose of the presentinvention, a solution of a homogenous mixture contains elements A, B andM in a ratio that is given by the formula A_(1-x)B_(x)M, wherein x is anumber defined by 0≦x<0.5.

[0078] In another embodiment of the present invention, one or morecarrier powders may be first slurry deposited to a solid support to forma washcoat according to methods known in the art. Then, solutions of thehomogenous mixtures of the present invention are impregnated into thepre-formed washcoat(s). After the catalyst impregnation, the supportbody is calcined in air at high temperature to form the desired phasechemistry. Examples of carrier powders that may be used to form awashcoat include, but are not limited to, titania, silica, alumina(transition and alpha-phase), ceria, zirconia, Ce_(1-x)Zr_(x)O₂, and allthe possible doped ceria formulations.

[0079] In accordance with one embodiment of the present invention, thewashcoat may contain not only carrier powders, but also perovskite-typecatalysts of the present invention. For example, bulk perovskite-typecatalysts of the present invention may be mixed with carrier powders tobe slurry deposited to a solid support to form a washcoat. Then,solutions of the homogenous mixtures may be impregnated into thewashcoat and calcined to form perovskite-type metal oxides on thewashcoat. In this embodiment, the washcoat may contain the bulkperovskite-type catalyst of the present invention and may also contain,optionally, ceria-based oxygen storage material and high-surface areagamma-alumina.

[0080] It is the discovery of the present invention that, not only thesolutions of the perovskite-type materials of the present invention maybe deposited into a washcoat containing a perovskite-type material,other non-perovskite-type catalysts may also be deposited to such awashcoat to achieve unexpected catalytic results. Accordingly, acatalytic converter of the present invention may also be formed bydepositing a non-perovskite-type catalyst into a washcoat of a supportwhich contains a perovskite-type material. In one embodiment of thepresent invention, the non-perovskite-type catalyst may be a base, or anoble metal, or a mixture thereof. Examples of a base metal catalystinclude, but are not limited to, metallic elements with atomic numbers3-4, 11-15, 19-32, 37-43, 48-52, 56-75, 80-83. Examples of noble metalcatalysts include, but are not limited to, elements with atomic numbers44, 45, 46, 47, 76, 77, 78 and 79.

[0081] The perovskite-type catalyst of the present invention has animproved three-way catalytic activity for the removal of unsaturated andsaturated hydrocarbons, nitrogen oxides and carbon monoxide from theexhaust gases of internal combustion engines, including small gasolineengines, and from industrial waste gases. They also exhibit high thermaland chemical stability. Further, they possess resistance to sulfurdioxide poisoning.

[0082] Accordingly, the perovskite-type catalysts of the presentinvention have a wide range of applications. For example, theperovskite-type catalysts of the present invention may be used forclean-up of exhaust emissions from all kinds of internal combustionengines. They may also be used in industrial catalysis for theproduction of industrial chemicals, fertilizers, and products in thepolymer and plastics field. They may further be used in all oil-derivedprocesses and products. They may also be used for clean-up of industrialprocess emissions including, but not limited to, volatile hydrocarbons,chlorinated hydrocarbons and MTBE.

[0083] In particular, the catalysts of the present invention may beused, for example, in the control of gaseous and particulate emissionsfrom all types of Otto cycle and Diesel cycle internal combustionengines (including Otto cycle lean-burn engines, Otto cycle and dieselcycle engines equipped with SCR capability with ammonia or hydrocarbonintake); olefin polymerization, hydrogenation reactions, methanolsynthesis from syngas (either carbon monoxide and hydrogen mixtures ormixtures also containing carbon dioxide); hydroformylation of alkenes;Fischer-Tropsch Synthesis; isomerization of hydrocarbons; aromizationreactions; catalytic cracking reactions; reactions involving the removalof Sulfur and/or Nitrogen and/or Oxygen from oil-derived hydrocarbons byhydrogenation; steam reforming of methanol and other hydrocarbons andhydrocarbon mixtures (e.g., gasoline) to produce gas mixtures containinghydrogen; the latter reactions where the hydrogen gas is used in afuel-cell; epoxidation of alkenes; partial and/or selective oxidation ofhydrocarbons; oxidation of volatile organic compounds (VOCs), includingMTBE.

[0084] It is known in the art that perovskite materials (powders, singlecrystals and thin films) containing Mn on the B-site show the giantmagnetoresistance effect. Because of this, the perovskite materials ofthe present invention having Mn on the B-site may also be used to makedevices such as magnetic recording heads or the like.

[0085] The following examples are intended to illustrate, but not tolimit, the scope of the invention. While the method described providesthe necessary information to make any given perovskite material of thepresent invention, typically those that might be used, other proceduresknown to those skilled in the art may alternatively be used.

Methods of Making Perovskite or Perovskite-Type Materials of the PresentInvention EXAMPLE 1

[0086] A single phase perovskite material of the nominal chemicalcomposition Ln_(0.6)Ca_(0.4)CoO₃ was synthesized by dissolving 104.15 gof mixed hydrated lanthanide carbonate, Ln₂.(CO₃)₃.4H₂O, in a solutionformed by dissolving 57.5 g of calcium nitrate tetrahydrate,Ca(NO₃)₂.4H₂O and 177.15 g of cobalt nitrate hexahydrate, Co(NO₃)₃ 6H₂O,into 2 liters of water. Intense stirring was used to form a solution ofall the components. The mixed lanthanide carbonate hydrate contains La,Ce, Pr and Nd. To this solution was added 200 g of malic acid. Thesolution was placed in a rotary evaporator and heated by a water bath.The water bath was heated to 90° C. The solution was reduced to 20% ofits original volume and had the consistency of a thick syrup. The syrupwas placed into a flat refractory tray and heat-treated at 200° C. for 1hr. The syrup was converted into a solid foam. The foam was thenheat-treated at a temperature of 700° C. in air for 2 hrs. with anintermediate grind after 1 hr. The product comprised a black powder ofthe noted chemical composition. X-ray diffraction analysis showed thematerial to be a single phase perovskite with a B.E.T. specific surfacearea of 13 m²/g.

[0087] The mixed hydrated lanthanide carbonate used herein is a singlephase compound crystallized from the La concentrate generated from thebastnasite ore. Therefore, it contained a modified ratio of Ln's. Thecerium concentration is about 4% on a lanthanide oxide basis.

[0088]FIG. 2 shows the measured X-ray diffraction intensity as afunction of two-theta when a perovskite material of compositionLn_(0.6)Ca_(0.4)CoO₃, made according to Example 1, is impinged by asource of monochromatic X-ray radiation. FIG. 2 shows that the compoundof Example 1 is a single phase perovskite material. All the peaks in thetrace can be indexed according to the crystal structure of theperovskite phase.

EXAMPLE 2

[0089] A single phase perovskite material of the same chemicalcomposition as in Example 1 was synthesized by dissolving 104.15 g ofmixed hydrated lanthanide carbonate, Ln₂.(CO₃)₃.4H₂O, in a solutionformed by dissolving 57.5 g of calcium nitrate tetrahydrate,Ca(NO₃)₂.4H₂O and 177.15 g of cobalt nitrate hexahydrate, Co(NO₃)₃.6H₂O,into 2 liters of water. Intense stirring was used to form a solution ofall the components. To this solution was added 200 g of malic acid. Thesolution was reduced to half its volume by heating at 80° C. on a hotplate for 3 hrs. The solution was then placed on a refractory tray andheated at 200° C. for 1 hr. The solid foam so obtained was heat-treatedat 700° C. in air for 2 hrs. with an intermediate grind after 1 hr. Theproduct comprised a black powder of the noted chemical composition andX-ray diffraction analysis showed the material to be a single phaseperovskite with a B.E.T. specific surface area of 13 m²/g.

EXAMPLE 3

[0090] A single phase perovskite material of the same composition as inExamples 1 and 2 was synthesized by grinding and homogenizing 52.08 g ofmixed hydrated lanthanide carbonate. 6.83 g of calcium oxide, CaO and22.82 g of cobalt oxide, CoO. The mixture was heated at 800° C. for 36hrs. in air with periodic regrinding. The product, comprising a blackpowder, was characterized by X-ray diffraction as being a single phaseperovskite compound with a B.E.T. surface area of 1.2 m²/g.

EXAMPLE 4

[0091] A single phase perovskite powder, as produced according toExample 1, was consolidated into pellets by using a uniaxial cold press.The pellets so produced were heat-treated at a range of heat treatmenttemperatures for a period of 1 hr. The pellets so heat-treated wereanalyzed by X-ray diffraction and the B.E.T. specific surface area wasmeasured. In each case, X-ray diffraction showed that the materialremained a single-phase perovskite material regardless of heat treatmenttemperature.

EXAMPLE 5

[0092] A single phase perovskite powder of the composition Ln₀ ₈₃Sr₀₁₇MnO₃ was synthesized according to the method illustrated in Example 2.The powder was made by dissolving 105.3 g of mixed hydrated lanthanidecarbonate, Ln₂(CO₃)₃ 4H₂O, 10.1 g of strontium nitrate, Sr(NO₃)₂ and 50g of hydrated manganese nitrate, Mn(NO₃)₂.6H₂O, into 2 liters of water.Malic acid was added to the solution and heat treatments were carriedout as in Example 2. The product comprised a black powder of the notedchemical composition and X-ray diffraction analysis showed the materialto be a single phase perovskite with a B.E.T. surface area of 9.3 m²/g.

EXAMPLE 6

[0093] A single-phase perovskite powder of composition Ln₀ ₇Sr₀ ₃CrO₃was synthesized according to the method illustrated in Example 2. Asolution was made by dissolving 23.48 g of mixed hydrated lanthanidecarbonate, Ln₂(CO₃)₃.4H₂O, 7.52 g of strontium nitrate. Sr(NO₃)₂, and 45g of hydrated chromium nitrate, Cr(NO₃)₃.9H₂O, into 1 liter of water. 60g of malic acid was added to the solution. Heat treatments were carriedout as in Example 2. A heat treatment temperature of 900° C. wasrequired to obtain a phase-pure, perovskite material. The product was anolive green powder with a B.E.T. surface area of 11.3 m²/g.

EXAMPLE 7

[0094] A single-phase perovskite powder of compositionLn_(0.6)Ca_(0.4)Fe_(0.8)Mn₀ ₂O₃ was synthesized according to the methodillustrated in Example 2. A solution was formed by dissolving 47.68 g ofmixed hydrated lanthanide carbonate, Ln₂(CO₃)₃.4H₂O, 26.50 g hydratedcalcium nitrate, Ca(NO₃)₂.4H₂O, 90.7 g of hydrated iron nitrate,Fe(NO₃)₃.9H₂O, and 17.93 g of hydrated manganese nitrate, Mn(NO₃)₂.6H₂O,into 2 liters of water. To this solution was added 130 g of malic acid.Heat treatments were carried out as in Example 2. The product was ablack, single-phase perovskite powder of the noted chemical composition,having a B.E.T. surface area of 32.1 m²/g.

EXAMPLE 8

[0095] A single phase perovskite material of compositionLn_(0.8)Sr_(0.2)Mn_(0.9)Ni₀ ₀₄Ru_(0.06)O₃ was synthesized. A solutionwas formed using 45.78 g of mixed hydrated lanthanide carbonate,Ln₂(CO₃)₃.4H₂O, 52.18 g of manganese nitrate hexahydrate, Mn(NO₃)₂.6H₂O,8.56 g of strontium nitrate, Sr(NO₃)₂, and 2.35 g of nickel nitratehexahydrate, Ni(NO₃).6H₂O in 1 liter of water. To the solution was added60 g of malic acid. This solution was reduced to half the originalvolume by heating on a hot plate for 3 hrs. The solution was convertedinto a solid foam as in Example 2. The solid foam so obtained was heatedat 350° C. for 2 hrs. and ground with 1.61 g of ruthenium oxide, RuO₂.This mixture was then heat-treated at 800° C. for 10 hrs. to produce asingle-phase perovskite powder of the desired composition with a B.E.T.surface area of 9.8 m²/g

EXAMPLE 9

[0096] A single-phase perovskite powder of composition Ln₀ ₈K₀₂Mn_(0.95)Ru_(0.05)O₃ was synthesized according to the methodillustrated in Example 8. A solution was formed by dissolving 52.17 g ofmixed hydrated lanthanide carbonate, Ln₂(CO₃)₃.4H₂O, 4.66 g of potassiumnitrate, KNO₃, and 62.77 g of hydrated manganese nitrate, Mn(NO₃)₂.6H₂O,in 2 liters of water. 110 g of malic acid was dissolved in thissolution. As illustrated in Example 8, RuO₂ was added to the foamedsolution after a heat treatment at 350° C. In this example, 1.53 g ofRuO₂ was added to the ground, heat-treated foam. This mixture washeat-treated at 70020 C. for 15 hrs. to produce a black, single-phaseperovskite powder of the noted composition and with a specific, B.E.T.surface area of 10.5 m²/g.

EXAMPLE 10

[0097] A single-phase perovskite powder of composition Ln₀ ₇Sr₀₃Cr_(0.95)Ru₀ ₀₅O₃ was synthesized according to the method illustratedin Example 8. A solution was formed by dissolving 39.27 g of mixedhydrated lanthanide carbonate, Ln₂(CO₃)₃.4H₂O, 12.57 g of strontiumnitrate, Sr(NO₃)₂, and 75.27 g of hydrated 1 chromium nitrate,Cr(NO₃)₃9H₂O, in 1.5 liters of water. To this solution, 82 g of malicacid was added. 1.32 g of RuO₂ was added to a powder comprising thefoamed solution that had been heat-treated at 350° C. This mixture wasthen heat-treated at 1000° C. for 32 hrs. to produce a dark brownsingle-phase perovskite powder of the noted composition. The B.E.T.surface area of the powder was 12.9 m²/g.

EXAMPLE 11

[0098] A single-phase perovskite of composition LnNiO₃ was synthesizedaccording to the method illustrated in Example 2. A solution was formedby dissolving 38.97 g of mixed hydrated lanthanide concentrate,Ln₂(CO₃)₃.4H₂O, and 40 g of hydrated nickel nitrate, Ni(NO₃)₂.6H₂O, to0.5 liters of water. Into this solution was dissolved 50 g of malicacid. Heat treatments were carried out as in Example 2. The black powderso obtained was a single-phase perovskite of the noted composition, witha specific surface area of 23.2 m²/g.

EXAMPLE 12

[0099] A single-phase powder with the perovskite-type “K₂NiF₄” structureof composition Ln₂(Cu_(0.6)Co_(0.2)Ni_(0.2))O₄ was synthesized accordingto the method illustrated in Example 2. A solution was formed bydissolving 50.0 g of mixed hydrated lanthanide concentrate,Ln₂(CO₃)₃.4H₂O, 12.32 g of hydrated copper nitrate, Cu(NO₃)₂.6H₂O, 5.13g of hydrated nickel nitrate, Ni(NO₃)₂.6H₂O, and 5.14 g of hydratedcobalt nitrate, Co(NO₃)₃.6H₂O, in 2 liters of water. Into this solutionwas dissolved 150 g of malic acid. Heat treatments were carried out asin Example 2. The black powder so obtained was a single-phase powderwith the “K₂NiF₄” structure of the noted composition and with a specificsurface area of 14.3 m²/g.

EXAMPLE 13

[0100] A single phase perovskite material of composition Ln₀ ₈K₀ ₂Mn₀₉₅Ru₀ ₀₅O₃ was synthesized according to the method illustrated inExample 9. A solution was formed by dissolving 50.3 g of a mixedhydrated lanthanide nitrate, Ln(NO₃)₃.4H₂O, 39.56 g of hydratedmanganese nitrate, Mn(NO₃)₂.6H₂O, and 2.94 g of potassium nitrate, KNO₃,in 1.5 liters of water. 51 g of citric acid was dissolved in thissolution. As illustrated in Example 9, RuO₂ was added to the foamedsolution after a heat treatment at 350° C. In this example, 0.96 g ofRuO₂ was added to the ground, heat-treated foam. This mixture washeat-treated at 70020 C. for 15 hrs. to produce a black, single-phaseperovskite powder of the noted composition with a B.E.T. surface area of12.2 m²/g.

[0101] The hydrated lanthanide nitrate is a single phase product ofcrystallization coming out of the solution of La concentrate generatedfrom the bastnasite ore. The product has a modified ratio of Ln's. Thecerium concentration on an oxide base is about 5% of the total Ln's.

EXAMPLE 14

[0102] A single phase perovskite material of compositionLn_(0.6)Ca_(0.4)Fe_(0.8)Mn_(0.2)O₃ was synthesized according to themethod illustrated in Example 2. A solution was formed by dissolving71.64 g of Ln carbonate, Ln₂(CO₃)₃.4H₂O, 39.75 g hydrated calciumnitrate, Ca(NO₃)₂.4H₂O, 136.05 g of hydrated iron nitrate,Fe(NO₃)₃.9H₂O, and 26.90 g of hydrated manganese nitrate, Mn(NO₃)₂.6H₂O,into 3 liters of water. To this solution was added 130 g of malic acid.Heat treatments were carried out as in Example 2. The product was ablack, single-phase perovskite powder of the noted chemical composition,having a B.E.T. surface area of 34.3 m²/g. The mixed hydrated Lncarbonate used in this example is a single phase compound frombastnasite concentration by acid dissolution process. It has a naturalratio of Ln's. Therefore, the cerium concentration reflects the naturalratio of cerium in any given bastnasite, i.e., it is slightly higherthan the La content on a LnO basis.

EXAMPLE 15

[0103] A single-phase perovskite material Ln₀₈Sr_(0.2)Mn_(0.9)Ni_(0.04)Pd₀ ₀₆O₃ was synthesized by dissolving 50.0 gof mixed hydrated lanthanide carbonate, Ln₂(CO₃)₃.4H₂O, in a solutionformed by dissolving 60.57 g of hydrated manganese nitrate,Mn(NO₃)₂.6H₂O, 9.92 g strontium nitrate, Sr(NO₃), 3.67 g hydratedpalladium nitrate, Pd(NO ₃).xH₂O (where x is about 1.7), and 2.73 gnickel nitrate, Ni(NO₃).6H₂O, into 1 liter of water. The mixed Lncompound contains La, Ce, Pr and Nd and is derived from bastnasite. Tothe solution that was formed, 194.0 g of malic acid was added anddissolved. This solution was dried at 190-310° C. for 1 hr. andheat-treated in a temperature range 500-1100° C. in air for 1-25 hrs.The product from any of these heat treatments was found to be asingle-phase perovskite powder. The surface area varied depending on theprecise heat treatment. The B.E.T. specific surface area was 8.2 m²/g ifthe heat treatment was 1000° C. for 16 hrs.

EXAMPLE 16

[0104] A single-phase perovskite materialLn_(0.8)Sr_(0.2)Mn_(0.9)Ni_(0.04)O₃ was synthesized according to themethod described in Example 15. The product was found to be asingle-phase perovskite powder. The surface area varied depending on theprecise heat treatment. The B.E.T. specific surface area was 9.4 m²/g ifthe heat treatment was 1000° C. for 16 hrs.

[0105] This composition was tested for its three-way catalyticconversion activity in a gas that closely simulates automobile exhaust.The catalyst was found to have reasonable three-way conversion activityover a range of redox potentials.

EXAMPLE 17

[0106] A single-phase perovskite material Ln₀ ₈Sr₀ ₂Mn₀ ₉Ni₀ ₀₄Ru₀ ₀₆O₃was synthesized according to the method described in Example 15.Appropriate quantities of the salt ruthenium nitrosyl nitrate were usedas the soluble ruthenium source. The product was found to be asingle-phase perovskite powder. The surface area varied depending on theprecise heat treatment. The B.E.T. specific surface area was 3.2 m²/g ifthe heat treatment was 1100° C. for 16 hrs.

EXAMPLE 18

[0107] A single-phase perovskite material Ln₀ ₇Sr₀₃Mn_(0.9)Ni_(0.04)Ru_(0.06)O₃ (Ln=low-Ce mixture of La, Ce, Pr and Nd)was synthesized by the method described in Example 15. The product fromheat treatments in air was found to be a single-phase perovskite powder.The surface area varied depending on the precise heat treatment.

[0108] This composition was tested for its three-way catalyticconversion activity in a gas that closely simulates automobile exhaust.The catalyst was found to have good three-way conversion activity over arange of redox potentials. The hydrocarbon and CO conversions inreducing gases were found to be superior to that of the materialdescribed in Example 15. It is clear that the catalyst is an efficientthree-way converter over a wide redox window, and thus, it is verysuitable for use in a three-way catalytic converter for the conversionof toxic emissions in combustion engine exhausts.

EXAMPLE 19

[0109] A single-phase perovskite material LnMn₀ ₅Cu₀ ₅O₃ was synthesizedaccording to the method described in Example 15. The product was foundto be a single-phase perovskite powder. The surface area varieddepending on the precise heat treatment. The B.E.T. specific surfacearea was 7.4 m²/g if the heat treatment was 1000° C. for 16 hrs.

[0110] This composition was tested for its three-way catalyticconversion activity in a gas that closely simulates automobile exhaust.The catalyst was found to have reasonable three-way conversion activityover a range of redox potentials.

EXAMPLE 20

[0111] A single-phase perovskite material LnMn_(0.8)Ni₀ ₁₀Cu_(0.10)O₃was synthesized according to the method described in Example 15. Theproduct was found to be a single phase perovskite powder. The surfacearea varied depending on the precise heat treatment. The B.E.T. specificsurface area was 10.1 m²/g if the heat treatment was 1000° C. for 16hrs.

[0112] This composition was tested for its three-way catalyticconversion activity in a gas that closely simulates automobile exhaust.The catalyst was found to have reasonable three-way conversion activityover a range of redox potentials.

EXAMPLE 21

[0113] In this example, a single-phase perovskite material was made intopowder and deposited onto a commercially available support structure. Asingle-phase perovskite materialLn_(0.8)Sr_(0.2)Mn_(0.9)Ni_(0.04)Pd_(0.06)O₃ was synthesized bydissolving 100 g of mixed hydrated lanthanide carbonate and 400 g ofmalic acid in a solution formed by dissolving 121.14 g of hydratedmanganese nitrate, 19.84 g of strontium nitrate, 29.76 g of 10.0 wt % Pdnitrosyl nitrate solution and 5.46 g of nickel nitrate hexahydrate and 2liters of water. The solution was dried and heat-treated at 800° C. for16 hrs. in air. The single-phase powder was then formed into a slurrywith water and 5% Dispural, and coated onto a 400 cells-per-square-inchcordierite honeycomb. After drying, the coated honeycomb washeat-treated at 70020 C. for 2 hrs. The loading of perovskite was in therange 5-25 g per liter of geometric volume of substrate. The three-wayperformance at stoichiometric air-fuel ratios at 400° C. is given by83.4% NOx, 92.1% CO and 85.2% THC.

EXAMPLE 22

[0114] In this example, a single-phase perovskite material in powderform was mixed with a carrier powder. A single-phase perovskite materialLn₀ ₈Sr₀ ₂Mn_(0.9)Ni_(0.04)Pd_(0.06)O₃ was synthesized by dissolving 100g of mixed hydrated lanthanide carbonate and 400 g of malic acid in asolution formed by dissolving 121.14 g of hydrated manganese nitrate,19.84 g of strontium nitrate, 29.76 g of 10.0 wt % Pd nitrosyl nitratesolution and 5.46 g of nickel nitrate hexahydrate and 2 liters of water.The solution was dried and heat-treated at 800° C. for 16 hrs. in air.The single-phase powder was then formed into a slurry by methods wellknown in the art, being mixed and milled with water, gamma-alumina,ceria-zirconia (Ce_(1-x)Zr_(x)O₂) and Dispural, and coated onto a 300cells-per-square-inch metal honeycomb substrate. The ratio of the foursolid ingredients in the slurry is being given by:perovskite/alumina/ceria-zirconia/dispural=8/70/20/2 wt %. After drying,the coated honeycomb was heat-treated at 700° C. for 2 hrs. The loadingof solids per liter of honeycomb was in the range 70-200 g. Thethree-way performance in perturbed exhaust gas streams, space velocity80,000 hr ⁻¹, with stoichiometric average air-fuel ratios at 400° C.after high temperature aging is given by 87.4% NOx, 95.1% CO and 88.2%THC.

EXAMPLE 23

[0115] In this example, a carrier powder was used to support anefficient low-cost catalyst. A solution with the cation compositionLn_(0.7)Sr_(0.3)Mn₀ ₉Pd_(0.1) was synthesized according to the previousexample. This solution was then impregnated into a gamma-alumina powderpreviously treated with bastnasite-derived mixed lanthanide nitratesolution and so having the formula Ln_(0.1)Al_(0.9)O₃. The powder atincipient wetness was then dried at 85° C. for 5 hrs. and heated at 200°C. for 5 hrs. and then finally at 900° C. for 16 hrs. The mixed powdercontained 6 wt % perovskite and possessed a high specific surface areaeven when heat-treated at 1100° C. for 20 hrs. The powder was thenloaded onto a cordierite honeycomb structure by first forming it into aslurry with 4% Dispural and water and acetic acid. The coated honeycombswere loaded to 120 g/L with the composite powder.

[0116] The temperature known as the light-off temperature—thetemperature above which the catalyst is functioning—was measured forNOx, CO and hydrocarbons as 315° C., 225° C. and 234° C., respectively,for a 100,000 hr⁻¹ space velocity.

EXAMPLE 24

[0117] In this example, pre-formed washcoats containing one or more ofthe carrier powders were used to support an efficient low-cost catalyst.A washcoat was formed onto a cordierite honeycomb support with 600cells-per-square-inch consisting of ceria-zirconia (25% zirconia) andgamma alumina in the weight ratio of 1:5. The washcoat loading was inthe range 50-250 g per liter. A solution with the cation compositionLn_(0.5)Sr_(0.5)Mn_(0.9)Pd_(0.1) (containing 100 g malic acid per literof solution) was impregnated into the washcoated honeycombs and thechannels blown clear of excess. The parts were dried and heat-treated attemperatures in the range of 500-1000° C. The perovskite catalystloading was in the 2-12 g/L range in the final part.

[0118] The catalysts were aged according to a 4-mode accelerated agingcycle simulating 100,000 miles of driving a car. The emissions from thetailpipe of a 4-cylinder gasoline powered automobile were 0.06 g/milehydrocarbons, 1.3 g/mile CO and 0.12 g/mile NOx. These emissionscorrespond to reductions compared to those from the tailpipe of 95% HC,83% CO and 96% NOx over the Federal Test Procedure drive cycle.

EXAMPLE 25

[0119] In this example, a pre-formed washcoat containing fully formedperovskite phases of the present invention was used to support anefficient low-cost catalyst. A washcoat was formed onto a cordieritehoneycomb support with 400 cells-per-square-inch consisting ofceria-zirconia (25% zirconia) and gamma alumina in the weight ratio of1:5: but also containing 10 wt % perovskite of formula Ln₀ ₈Sr_(0.2)MnO₃. The washcoat loading was in the range 50-150 g per liter.A solution with the cation composition Ln_(0.5)Sr₀ ₅Mn_(0.98)Pd_(0.02)(containing 100 g malic acid per liter of solution) was impregnated intothe washcoated honeycombs and the channels blown clear of excess. Theparts were dried and heat-treated at temperatures in the range of600-900° C. The perovskite catalyst Ln_(0.5)Sr_(0.5)Mn_(0.98)Pd_(0.02)O₃was loaded in the 5-20 g/L range in the final part.

[0120] The catalysts were aged according to a 2-mode accelerated agingcycle simulating 50,000 miles of driving a car and then tested on abench reactor with simulated car exhaust. The transient conversionefficiencies of NOx, CO and HC, at 400° C. and 100,000 hr⁻¹ spacevelocity, were measured as 78%, 88% and 93%, respectively.

EXAMPLE 26

[0121] In this example, a pre-formed washcoat was used as a carrier. Awashcoat was formed onto a cordierite honeycomb support with 400cells-per-square-inch consisting of ceria-zirconia and perovskite offormula Ln₀ ₈Sr₀ ₂MnO₃ in equal weight proportions. The washcoat loadingwas in the range 50-100 g per liter. A solution with the cationcomposition Ln₀ ₈Sr₀ ₂Mn₀ ₉₆Pd₀ ₀₄ (containing 100 g malic acid perliter of solution) was impregnated into the washcoated honeycombs andthe channels blown clear of excess. The parts were dried andheat-treated at temperatures in the range of 600-900° C. The perovskitecatalyst Ln_(0.8)Sr₀ ₂ Mn₀ ₉₆Pd₀ ₀₄O₃ was loaded in the 5-10 g/L rangein the final part.

[0122] The catalysts were aged according to a 2-mode accelerated agingcycle simulating 50,000 miles of driving a car and then tested on abench reactor with simulated car exhaust. The transient conversionefficiencies of NOx, CO and HC, at 400° C. and 12,000 hr⁻¹ spacevelocity, were measured as 81%, 86% and 95%, respectively.

EXAMPLE 27

[0123] In this example, high surface area inert powders were used tosupport an efficient low-cost catalyst. A single-phase perovskitematerial Ln₀ ₈Sr_(0.2)Mn_(0.9)Ni_(0.04)Pd_(0.06)O₃ was synthesized bydissolving 100 g of mixed hydrated lanthanide carbonate and 400 g ofmalic acid in a solution formed by dissolving 121.14 g of hydratedmanganese nitrate, 19.84 g of strontium nitrate, 29.76 g of 10.0 wt % Pdnitrosyl nitrate solution and 5.46 g of nickel nitrate hexahydrate and 2liters of water. The solution was dried and heat-treated at 800° C. for16 hrs. in air. The single-phase powder was then formed into a slurry bymethods well known in the art, being mixed and milled with water,gamma-alumina, ceria-zirconia (Ce_(1-x)Zr_(x)O₂) and Dispural, andcoated onto a 300 cells-per-square-inch metal honeycomb substrate. Theratio of the four solid ingredients in the slurry is being given by:perovskite/alumina/ceria-zirconia/dispural=8/70/20/2 wt %. After drying,the coated honeycomb was heat-treated at 70020 C. for 2 hrs. The loadingof solids per liter of honeycomb was in the range 70-200 g. Thethree-way performance in perturbed exhaust gas streams, space velocity80,000 hr⁻¹, with stoichiometric average air-fuel ratios at 400° C.after high temperature aging, is given by 87.4% NOx, 95.1% CO and 88.2%THC.

EXAMPLE 28

[0124] A washcoat was formed onto a cordierite honeycomb support with600 cells-per-square-inch consisting of ceria-zirconia (25% zirconia)and gamma alumina in the weight ratio of 1:5. The washcoat loading wasin the range 50-250 g per liter. A solution with the cation compositionLn₀ ₅Sr_(0.5)Mn_(0.95)Pt₀ ₀₅ (containing 100 g malic acid per liter ofsolution) was impregnated into the washcoated honeycombs and thechannels blown clear of excess. The parts were dried and heat-treated attemperatures in the range of 500-1000° C. The perovskite catalystloading was in the 2-12 g/L range in the final part.

[0125] The catalysts were aged according to a 4-mode accelerated agingcycle simulating 100,000 miles of driving a car. The emissions from thetailpipe of a 4-cylinder gasoline powered automobile were 0.06 g/milehydrocarbons, 1.3 g/mile CO and 0.12 g/mile NOx. These emissionscorrespond to reductions compared to those from the tailpipe of 95% HC,93% CO and 78% NOx over the Federal Test Procedure drive cycle.

EXAMPLE 29

[0126] A single-phase perovskite materialLn_(0.8)Sr_(0.2)Mn_(0.92)Ni_(0.05)Pd_(0.03)O₃ was synthesized bydissolving the appropriate amounts of mixed hydrated lanthanidecarbonate, malic acid, hydrated manganese nitrate, strontium nitrate, Pdnitrosyl nitrate solution and nickel nitrate hexahydrate and 2 liters ofwater. The solution was dried and heat-treated at 800° C. for 16 hrs. inair. The single-phase powder was then formed into a slurry with waterand 5% Dispural, and coated onto a 400 cells-per-square-inch cordieritehoneycomb. After drying, the coated honeycomb was heat-treated at 70020C. for 2 hrs. The loading of perovskite was in the range 15-25 g perliter of geometric volume of substrate. With a loading of 21 g/L, thethree-way performance at stoichiometric air-fuel ratios at 400° C. isgiven by 80.4% NOx, 91.1% CO and 84.2% THC.

EXAMPLE 30

[0127] A solution of cation composition Ln_(0.8)Sr_(0.2)Mn₀ ₉₄Pt₀₀₅Rh_(0.01)O_(3±d), was formed using the salts mentioned in the previousexample, in addition to DPN and rhodium chloride. The solution wasimpregnated into a washcoat consisting of ceria-zirconia (25% zirconia)and gamma alumina in the weight ratio of 1:5. The washcoat waspre-formed onto a cordierite honeycomb support with 400cells-per-square-inch with a loading of 125 g per liter. The impregnatedpart was dried at 150° C. and heat-treated at 650° C. for 5 hrs. Theloading of catalyst was measured as 4 g per liter of catalyst. Thethree-way performance in perturbed exhaust gas streams, space velocity80,000 hr⁻¹, with stoichiometric average air-fuel ratios at 400° C.after high temperature aging is given by 93.4% NOx, 94.1% CO and 87.2%THC.

EXAMPLE 31

[0128] A washcoat was formed onto a cordierite honeycomb support with600 cells-per-square-inch consisting of ceria-zirconia (25% zirconia)and gamma alumina in the weight ratio of 1:5. The washcoat loading wasin the range 100-120 g per liter. A solution with the cation compositionLn_(0.8)Ba_(0.2)Mn_(0.94)Pd_(0.06) (containing 100 g malic acid perliter of solution) was impregnated into the washcoated honeycombs andthe channels blown clear of excess. The parts were dried andheat-treated at temperatures in the range of 700-750° C. The perovskitecatalyst loading was in the 4-6 g/L range in the final part.

[0129] The catalysts were aged according to a 4-mode accelerated agingcycle simulating 50,000 miles of driving a car. The light-offtemperatures after aging were measured to be 280° C. for HC, 274° C. forCO and 310° C. for NOx.

EXAMPLE 32

[0130] In this example, a solution with the cation composition Ln₀ ₅Sr₀₅Mn₀ ₉₈Rh₀ ₀₂O_(3±d) was synthesized. This solution was then impregnatedinto a gamma-alumina powder previously treated with bastnasite-derivedmixed lanthanide nitrate solution and so having the formula Ln_(0.1)Al₀₉O₃. The powder at incipient wetness was then dried at 85° C. for 5 hrs.and heated at 200° C. for 5 hrs. and then finally at 90020 C. for 16hrs. The mixed powder contained 4 wt % perovskite and possessed a highspecific surface area even when heat-treated at 1100° C. for 20 hrs. Thepowder was then loaded onto a cordierite honeycomb structure by firstforming it into a slurry with 4% Dispural and water and acetic acid. Thecoated honeycombs were loaded to 120 g/L with the composite powder.

[0131] The temperature known as the light-off temperature—thetemperature above which the catalyst is functioning—was measured forNOx, CO and hydrocarbons as 243° C., 264° C. and 274° C., respectively,for a 100,000 hr⁻¹ space velocity.

EXAMPLE 33

[0132] In this example, a single-phase perovskite materialLn_(0.8)Sr_(0.2)Co_(0.9)Ru_(0.1)O₃ was synthesized by the methoddescribed in Example 9. The solution was dried and heat-treated at 800°C. for 16 hrs. in air. The single-phase powder was then formed into aslurry by methods well known in the art, being mixed and milled withwater, gamma-alumina, ceria-zirconia (Ce_(1-x)Zr_(x)O₂) and Dispural,and coated onto a 300 cells-per-square-inch metal honeycomb substrate.The ratio of the four solid ingredients in the slurry is being given by:perovskite/alumina/ceria-zirconia/dispural=20/56/20/4 wt %. Afterdrying, the coated honeycomb was heat-treated at 70020 C. for 2 hrs. Theloading of solids per liter of honeycomb was in the range 70-200 g. Thethree-way performance in perturbed exhaust gas streams, space velocity40,000 hr⁻¹, with stoichiometric average air-fuel ratios at 550° C.after high temperature aging is given by 89.4% NOx, 93.1% CO and 90.2%THC.

EXAMPLE 34

[0133] In this example, a single-phase perovskite materialLn_(0.8)Sr_(0.2)Mn₀ ₉Ru₀ ₁O₃ was synthesized by the method described inExample 8. The solution was dried and heat-treated at 800° C. for 16hrs. in air. The single-phase powder was then formed into a slurry bymethods well known in the art, being mixed and milled with water,gamma-alumina, ceria-zirconia (Ce_(1-x)Zr_(x)O₂) and Dispural, andcoated onto a 300 cells-per-square-inch metal honeycomb substrate. Theratio of the four solid ingredients in the slurry is being given by:perovskite/alumina/ceria-zirconia/dispural=15/60/20/5 wt %. Afterdrying, the coated honeycomb was heat-treated at 750° C. for 2 hrs. Theloading of solids per liter of honeycomb was in the range 100-150 g. Thethree-way performance in perturbed exhaust gas streams, space velocity40,000 hr⁻¹, with stoichiometric average air-fuel ratios at 500° C.after high temperature aging is given by 91.4% NOx, 83.0% CO and 86.2%THC.

EXAMPLE 35

[0134] A washcoat was formed onto a cordierite honeycomb support with600 cells-per-square-inch consisting of ceria-zirconia (25% zirconia)and gamma alumina in the weight ratio of 1:5. The washcoat loading wasin the range 50-250 g per liter. A solution with the cation compositionLn_(0.5)Sr_(0.5)Mn_(0.96)Pd_(0.05) (containing 100 g malic acid perliter of solution) was impregnated into the washcoated honeycombs andthe channels blown clear of excess. The parts were dried andheat-treated at temperatures in the range of 600-1000° C. The perovskitecatalyst loading was in the 2-12 g/L range in the final part. A secondsolution with the cation composition Ln_(0.5)Sr₀ ₅Co₀ ₉₅Ru₀ ₀₅(containing 100 g malic acid per liter of solution) was impregnated intothe washcoated and solution-impregnated honeycombs and the channelsblown clear of excess. The parts were dried and heat-treated attemperatures in the range of 600-1000° C. The second perovskite catalystloading was in the 4-10 g/L range in the final part.

[0135] The catalysts were aged according to a 4-mode accelerated agingcycle simulating 50,000 miles of driving a car. The emissions from thetailpipe of a 4-cylinder gasoline powered automobile were 0.09 g/milehydrocarbons, 1.6 g/mile CO and 0.09 g/mile NOx.

[0136] This catalyst also displayed good poison resistance to sulfur,maintaining stoichiometric and rich-of-stoichiometric NOx conversionefficiency in excess of 99% at 500° C.

EXAMPLE 36

[0137] This example shows that a non-perovskite-type catalyst may beimpregnated into a washcoat containing a perovskite-type catalyst. Inthis example, a non-perovskite-type catalyst of formula Sr₂Pd_(0.1)O_(x)is impregnated into a pre-formed carrier coating comprising aperovskite-type material Ln_(0.5)Sr_(0.5)MnO₃. The carrier coating alsocontains Ce_(0.75)Zr_(0.25)O₂ and gamma-alumina. The ratio of the threeconstituents of the coating is 20 wt % Ln_(0.5)Sr₀ ₅MnO₃, 20 wt %Ce_(0.75)Zr₀ ₂₅O₂ and 60 wt % gamma-alumina. The carrier coating isformed onto a ceramic honeycomb with a cell density of 400cells-per-square-inch at a loading of 120 g per liter of substrate bythe slurry-coating technique well known in the art. A nitrate solutionwith the cation composition Sr₂Pd_(0.1) is formed from the appropriatenitrate precursors and water. The catalyst solution is then impregnatedinto the coated honeycomb, dried and calcined at 800° C. for 2 hrs. ThePd concentration in the heat-treated catalyst is 0.2 g per liter. Thethree-way performance at stoichiometric air-fuel ratios at 400° C. afteraging at 950° C. for 20 hrs. is given by 90.4% NOx, 98.2% CO and 96.3%THC.

EXAMPLE 37

[0138] A washcoat was formed onto a cordierite honeycomb support with300-cells-per-square-inch consisting of ceria-zirconia (25% zirconia)and gamma alumina in the weight ratio of 1:5. The washcoat loading wasin the range 120-140 g per liter. A solution with the cation compositionLn₀ ₅Sr₀ ₅Mn_(0.95)Pd_(0.05) (containing 100 g malic acid per liter ofsolution) was impregnated into the washcoated honeycombs and thechannels blown clear of excess. The parts were dried and heat-treated attemperatures in the range of 700-90020 C. The perovskite catalystloading was in the 4-6 g/L range in the final part. A second solutionwith the cation composition Ln_(0.5)Sr_(0.5)Mn₀ ₉₅Ru₀ ₀₅ (containing 100g malic acid per liter of solution) was impregnated into the washcoatedand solution-impregnated honeycomb and the channels blown clear ofexcess. The parts were dried and heat-treated at temperatures in therange of 700-800° C. The second perovskite catalyst loading was in the3-4 g/L range in the final part.

[0139] The catalysts were aged according to a 2-mode, fuel-cut,accelerated aging cycle simulating 50,000 miles of driving a car. Thethree-way conversion efficiency at typical operating temperatures wasmeasured as 98.1% hydrocarbons, 91.2% CO and 96.7% NOx.

[0140] This catalyst also displayed good poison resistance to sulfur,maintaining stoichiometric and rich-of-stoichiometric NOx conversionefficiency in excess of 95% at 500° C.

Three-Way Catalytic Activities of Perovskite Materials of the PresentInvention EXAMPLE 38

[0141] Perovskite-type materials made according to the present inventionare measured for their three-way catalytic activities. FIG. 3 shows theconversion percentages, catalyzed by a perovskite material ofcomposition Ln₀ ₈K₀ ₂Mn₀ ₉₅Ru₀ ₀₅O₃ as described in Example 9, for theconversion of NO, HC and CO from a gas mixture simulating automobileexhausts with varying oxygen content. The space velocity of the gas was33,000 h⁻¹ and the temperature of the perovskite catalyst bed was heldat a temperature of 550° C. The redox potential of the gas, R, isapproximated by {3C_(HC)+C_(CO)}/{C_(NO)+2C₀₂), wherein C represents theconcentration of the gases. In general, when R>1, the gas is classifiedas a reducing gas which is generated by a fuel-rich exhaust. When R<1,the gas is classified as an oxidizing gas which is generated byfuel-lean exhaust. In addition to these four gases, namely CO, C₃H₆, NOand O₂, carbon dioxide and steam were also present in the gas mixture.

[0142] For a gas mixture which is typical of engine exhaust from themiddle of the range of air-fuel ratios (R=1.02), the material shows goodthree-way conversion. Conversions of CO, NO and HC were 83.1, 94.4 and99.6, respectively. With fuel-rich gases (R=1.086, R=1.17) the materialalso displayed excellent three-way conversion. This is unusual and is aunique feature of the mixed-valence oxide materials, and is also relatedto the Ce on the A-site for fuel-rich gases. The conversion of COdropped fractionally below 80%, the conversion of the HC was above 90%and the conversion of NO approached 100% (the output NO level wasmeasured less than 10 ppb). For gases simulating lean fuel-air mixtures(R=0.86), the NO conversion was below 10%. The CO conversion was above90% and the HC conversion was above 50%. The low conversion of NO inoxidizing gases is well known and is a direct consequence of thefundamental nature of the NO reduction process and the redox potentialof this gas.

[0143] The whole data set was highly reproducible; the gas mixture couldbe cycled between “rich” (R=1.17) and “lean” (R=0.86) with repeatableconversions for all three critical gases. In addition, the conversionperformance for a particular gas (a given R) was not a function of thehistory of the sample testing, e.g., which type of gas was run first,etc. This is significant since a lot of the previous work on these typesof materials were plagued by hysterisis effects. Such effects wouldpreclude any realistic application of these materials in technologicalapplications.

[0144] In conclusion, FIG. 3 shows that the material made according tothe present invention is active as a “three-way catalyst” withparticularly effective performance at the rich end of the operatingwindow (commonly used in closed-loop, three-way catalytic converters).This superior rich performance is attributed to the presence of a mixedlanthanide A-site in the perovskit; in particular, it can be attributedto the presence of Ce on the A-site of the perovskite phase. It isunderstood that the materials made according to the present inventioncontain at least about 4% of CeO₂ on a LnO basis.

EXAMPLE 39

[0145] The temperature at which catalytic converter materials becomeactive is very important technologically and is commonly referred to asthe “light-off” temperature. The catalytic activity of the material ismonitored as the catalyst bed is progressively heated up from ambienttemperatures.

[0146]FIG. 4 shows the light-off behavior of the material for a reducinggas mixture (R=1.17) with a space velocity of 61,300 h⁻¹. Attemperatures below 300° C. the material showed no conversion activity.In the temperature window of 300° C. to 400° C., there was a rapidincrease of conversion activity with temperature. At 500° C. and above,conversion activities for NO and HC were high (greater than 99.9% and97.0%, respectively). This high activity was maintained up to themaximum testing temperature of 90020 C. The CO conversion activitieswere slightly lower than the levels measured in the previous test (FIG.3: conversion of CO at T=550° C. and R=1.17 was measured at 82.1%,whereas the corresponding conversion in this test, FIG. 4, isapproximately 75%). There is a significant decrease in CO conversionactivity as temperatures are increased above 500° C. One possible causeof this decrease in CO conversion activity is the relatively high spacevelocity used in these measurements compared to that used in the earliermeasurements (61,300 h⁻¹ vs. 33,000 h⁻¹).

[0147] In conclusion, FIG. 4 shows that (1) the catalytic activity ofthe material is good at high temperatures (90020 C.), and (2) there isappreciable activity significantly below the usual operating temperaturerange for a traditional catalytic converter (500° C.-700° C.). In otherwords, the material shows a considerable cold-start function.

EXAMPLE 40

[0148] The composition of Example 15 was tested for its three-waycatalytic conversion activity in a gas that closely simulates automobileexhaust. FIG. 5 shows the three-way activity for 0.5 g (occupying about1 cc in volume) of the above perovskite composition in an exhaust gasflow rate of approximately 1 liter/min. The gas composition was 150cc/min steam, 210 cc/min carbon dioxide, 13.5 cc/min CO, 1.5 cc/min NO,0.75 cc/min propene and variable oxygen content. The oxygen content wasvaried to explore the conversion efficiency over a wide range of redoxpotential, R. The bed temperature was 550° C.

[0149] It is clear that the catalyst is an efficient three-way converterover a wide redox window Therefore, it is very suitable for use in athree-way catalytic converter for the conversion of toxic emissions incombustion engine exhausts.

EXAMPLE 41

[0150] This composition of Example 17 was tested for its three-waycatalytic conversion activity in a gas that closely simulates automobileexhaust. FIG. 6 shows the three-way activity for 0.5 g (occupying about1 cc in volume) of the above perovskite composition in an exhaust gasflow rate of approximately 1 liter/min. The gas composition was 150cc/min steam, 210 cc/min carbon dioxide, 13.5 cc/min CO, 1.5 cc/min NO,0.75 cc/min propene and variable oxygen content. The oxygen content wasvaried to explore the conversion efficiency over a wide range of redoxpotential, R. The bed temperature was 550° C. The catalyst was found tohave good three-way conversion activity over a range of redoxpotentials. It is clear that the catalyst is an efficient three-wayconverter over a wide redox window, and thus, it is very suitable foruse in a three-way catalytic converter for the conversion of toxicemissions in combustion engine exhausts.

[0151] The excellent thermal stability of this composition was shown byx-ray diffraction (XRD) on powder samples before and after treatment inthe reducing exhaust gas at 1000° C. for 5 hrs. There was no noticeabledecomposition of the perovskite phase to reduced perovskite phases ordecomposition of the perovskite phase altogether.

[0152] The present invention may be embodied in other specific formswithout departing from its essential characteristics. The describedembodiment is to be considered in all respects only as illustrative andnot as restrictive. The scope of the present invention is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range of theequivalence of the claims are to be embraced within their scope.

What is claimed is:
 1. A perovskite-type catalyst consisting essentiallyof a metal oxide composition represented by the general formula:A_(1-x)B_(x)MO₃ wherein A is a mixture of elements originally in theform of a single phase mixed lanthanide collected from bastnasite; B isa divalent or monovalent cation; M is at least one element selected fromthe group consisting of elements of an atomic number of from 22 to 30,40 to 51, and 73 to 80; and x is a number defined by 0≦x<0.5.
 2. Aperovskite-type catalyst of claim 1 having a formula Ln₀ ₅Sr_(0.5)Mn₀₉₅Pt₀ ₀₅O₃
 3. A perovskite-type catalyst of claim 1 having a formulaLn_(0.8)Sr_(0.2)Mn_(0.92)Ni_(0.05)Pd_(0.03)O₃.
 4. A perovskite-typecatalyst of claim 1 having a formula Ln_(0.8)Sr_(0.2)Mn₀ ₉₄Pt_(0.05)Rh₀₀₁O₃.
 5. A perovskite-type catalyst of claim 1 having a formulaLn_(0.8)Ba_(0.2)Mn_(0.94)Pd_(0.06)O₃
 6. A perovskite-type catalyst ofclaim 1 having a formula Ln₀ ₅Sr_(0.5)Mn_(0.98)Rh_(0.02)O₃.
 7. Aperovskite-type catalyst of claim 1 having a formula Ln₀ ₈Sr₀ ₂Co₀₉Ru_(0.1)O₃.
 8. A perovskite-type catalyst of claim 1 having a formulaLn₀ ₈Sr₀ ₂Mn₀ ₉Ru_(0.1)O₃.
 9. A perovskite-type catalyst of claim 1having a formula Ln₀ ₈Sr₀ ₂Mn_(0.9)Ni₀ ₀₄Pd₀ ₀₆O₃
 10. A perovskite-typecatalyst of claim 1 having a formula Ln₀ ₇Sr₀ ₃Mn_(0.9)Pd_(0.1)O₃
 11. Aperovskite-type catalyst of claim 1 having a formula Ln₀ ₅Sr₀ ₅Mn₀ ₉Pd₀₁O₃.
 12. A perovskite-type catalyst of claim 1 having a formula Ln₀ ₅Sr₀₅Mn₀ ₉₈Pd_(0.02)O₃
 13. A perovskite-type catalyst of claim 1 having aformula Ln₀ ₈Sr₀ ₂ MnO₃.
 14. A catalytic converter comprises: (a) aperovskite-type catalyst comprising a metal oxide compositionrepresented by the general formula: A_(1-x)B_(x)MO₃ wherein A is amixture of elements originally in the form of a single phase mixedlanthanide collected from bastnasite; B is a divalent or monovalentcation; M is at least one element selected from the group consisting ofelements of an atomic number of from 22 to 30, 40 to 51, and 73 to 80; xis a number defined by 0≦x<0.5; and (b) a structure for supporting thecatalyst.
 15. The catalytic converter of claim 14, wherein the structureis a honeycomb support.
 16. The catalytic converter of claim 15, whereinthe honeycomb support is a ceramic honeycomb support.
 17. The catalyticconverter of claim 15, wherein the honeycomb support is a metalhoneycomb support.
 18. The catalytic converter of claim 14, wherein thestructure is in the form of beads or pellets.
 19. The catalyticconverter of claim 14, wherein the perovskite-type catalyst has aformula selected from a group consisting ofLn_(0.5)Sr_(0.5)Mn_(0.95)Pt_(0.05)O₃,Ln_(0.8)Sr_(0.2)Mn_(0.92)Ni_(0.05)Pd_(0.03)O₃,Ln_(0.8)Sr_(0.2)Mn_(0.94)Pt_(0.05)Rh_(0.01)O₃,Ln_(0.8)Ba_(0.2)Mn_(0.94)Pd_(0.06)O₃,Ln_(0.5)Sr_(0.5)Mn_(0.98)Rh_(0.02)O₃, Ln₀ ₈Sr_(0.2)Co_(0.9)Ru_(0.1)O₃,Ln_(0.8)Sr_(0.2)Mn_(0.9)Ru_(0.1)O₃. Ln_(0.8)Sr_(0.2)Mn₀ ₉Ni₀₀₄Pd_(0.06)O₃. Ln_(0.7)Sr₀ ₃Mn_(0.9)Pd₀ ₁O₃. Ln_(0.5)Sr₀ ₅Mn₀₉Pd_(0.1)O₃. Ln_(0.5)Sr_(0.5)Mn₀ ₉₈Pd₀ ₀₂ O₃. Ln_(0.8)Sr₀ ₂MnO₃, and amixture thereof.
 20. The catalytic converter of claim 14 furthercomprises a carrier powder.
 21. The catalytic converter of claim 20,wherein the carrier powder is an inert powder.
 22. The catalyticconverter of claim 21, wherein the inert powder is a gamma-aluminapowder, a ceria-based powder, or a mixture thereof.
 23. The catalyticconverter of claim 20, wherein the carrier powder is selected from agroup consisting of titania, silica, gamma alumina, alpha alumina,ceria, zirconia, ceria-zirconia, and a mixture thereof.
 24. Thecatalytic converter of claim 20, wherein the carrier powder is a mixtureof at least two different carrier powders.
 25. The catalytic converterof claim 24, wherein the carrier powder is a ceria-alumina mixture. 26.The catalytic converter of claim 14, wherein the perovskite-typecatalyst is in a bulk form.
 27. The catalytic converter of claim 20,wherein the perovskite-type catalyst is in a bulk form.
 28. Thecatalytic converter of claim 27, wherein the perovskite-type catalyst ismixed with the carrier powder to form a stable slurry suspension, andthen the suspension is deposited on the support.
 29. The catalyticconverter of claim 20, wherein the perovskite-type catalyst is in theform of a dispersion.
 30. The catalytic converter of claim 29, whereinthe method of forming the dispersed catalyst comprises the steps of: (a)forming a homogeneous solution of a single phase mixed lanthanide saltof element A and respective salts or oxides of elements B and M, whereinthe ratio of A:B:M is the same as their ratio in the formulaA_(1-x)B_(x)M as defined in claim 14; (b) impregnating the solution tothe carrier powder; and (c) calcining the carrier powder impregnatedwith the solution of step (a) to form the perovskite-type catalyst inthe form of a dispersion.
 31. The catalytic converter of claim 30comprising at least two different perovskite-type catalysts in adispersion form, wherein the dispersed perovskite-type catalysts areslurry deposited onto the support individually, in combinations, orsequentially.
 32. The catalytic converter of claim 31, wherein the twodifferent perovskite-type catalysts are a perovskite-type catalyst witha formula Ln₀ ₅Sr₀ ₅Mn₀ ₉₅Pd₀ ₀₅O₃ and a perovskite-type catalyst with aformula Ln₀ ₈Sr₀ ₂Co₀ ₉Ru_(0.1)O₃.
 33. The catalytic converter of claim31, wherein the two different perovskite-type catalysts are aperovskite-type catalyst with a formula Ln₀ ₅Sr_(0.5)Mn₀ ₉₅Pd₀ ₀₅O₃ anda perovskite-type catalyst with a formula Ln₀ ₅Sr₀ ₅Mn₀ ₉₅Ru_(0.05)O₃.34. The catalytic converter of claim 20 comprising a perovskite-typecatalyst in a bulk form, wherein the carrier powder and bulk catalystare slurry deposited as a washcoat on the support.
 35. The catalyticconverter of claim 34 further comprising a second perovskite-typecatalyst in the form of a dispersion, wherein the second catalyst isdispersed on the washcoat of the support.
 36. The catalytic converter ofclaim 35, wherein the first and second catalysts have the same ordifferent formula.
 37. The catalytic converter of claim 36, wherein thefirst catalyst is Ln_(0.8)Sr_(0.2)MnO₃, and the second catalyst isLn_(0.5)Sr_(0.5)Mn_(0.98)Pd_(0.02)O₃.
 38. The catalytic converter ofclaim 32 further comprising a second catalyst in the form of adispersion, and the second catalyst is dispersed in the washcoatcontaining the bulk perovskite-type catalyst.
 39. The catalyticconverter of claim 38, wherein the second catalyst is a single base, anoble metal, or a mixture thereof.
 40. The catalytic converter of claim39, wherein the single base metal is selected from a group consisting ofmetallic elements with atomic numbers 3-4, 11-15, 19-32, 37-43, 48-52,56-75, 80-83.
 41. The catalytic converter of claim 39, wherein the noblemetal is selected from a group consisting of elements with atomicnumbers 44, 45, 46, 47, 76, 77, 78 and
 79. 42. The catalytic converterof claim 39, wherein the second catalyst is the oxide of Sr₂Pd_(0.1).43. A method of making a catalytic converter comprising the steps of:(a) providing a perovkite-type catalyst comprising a metal oxidecomposition represented by the general formula: A_(1-x)B_(x)MO₃ whereinA is a mixture of elements originally in the form of a single phasemixed lanthanide collected from bastnasite; B is a divalent ormonovalent cation; M is at least one element selected from the groupconsisting of elements of an atomic number of from 22 to 30, 40 to 51,and 73 to 80; x is a number defined by 0≦x<0.5; and (b) providing asupport structure having a surface; (c) forming a stable slurrysuspension of the perovskite-type catalyst; and (d) depositing thesuspension of the perovskite-type catalyst on the surface of the supportstructure.
 44. The method of making a catalytic converter of claim 43,wherein the perovskite-type catalyst is in a bulk form.
 45. The methodof making a catalytic converter of claim 44 which further comprises thesteps of providing a carrier powder and mixing the carrier powder intothe stable slurry suspension of step (b).
 46. The method of making acatalytic converter of claim 45, wherein the carrier powder is an inertpowder.
 47. The method of making a catalytic converter of claim 46,wherein the inert powder is a gamma-alumina powder, a ceria-basedpowder, or a mixture thereof.
 48. The method of making a catalyticconverter of claim 45, wherein the carrier powder is selected from agroup consisting of titania, silica, gamma alumina, alpha alumina.ceria, zirconia, ceria-zirconia, and a mixture thereof.
 49. The methodof making a catalytic converter of claim 43, wherein the perovskite-typecatalyst is in a form of dispersion.
 50. The method of making acatalytic converter of claim 49, wherein the dispersion form of theperovskite-type catalyst is formed by the steps of: (a) forming ahomogeneous solution of a single phase mixed lanthanide salt of elementA collected from bastnasite and respective salts or oxides of elements Band M, wherein the ratio of A:B:M is the same as their ratio in theformula A_(1-x)B_(x)M as defined in claim 43; (b) impregnating thesolution to a carrier powder; and (c) calcining the carrier powderimpregnated with the solution of step (a) to form the perovskite-typecatalyst in the form of a dispersion.
 51. The method of making acatalytic converter of claim 50, wherein the carrier powder is selectedfrom a group consisting of titania, silica, gamma alumina, alphaalumina, ceria, zirconia, ceria-zirconia, and a mixture thereof.
 52. Themethod of claim 45, wherein the bulk perovskite-type catalyst and thecarrier powder is slurry deposited onto the support as a layer ofwashcoat.
 53. The method of making a catalytic converter of claim 52further comprising the steps of: (a) forming a homogeneous solution of asingle phase mixed lanthanide salt of element A collected frombastnasite, and respective salts or oxides of elements B and M, whereinthe ratio of A:B:M is the same as their ratio in the formulaA_(1-x)B_(x)M as defined in claim 43; (b) impregnating the solution ontothe washcoat of the support, wherein the support is pre-coated with thecarrier power and bulk perovskite-type catalyst by slurry deposition;and (c) calcining the pre-coated support impregnated with the solutionto form a perovskite-type metal oxide on the pre-coated support.
 54. Themethod of making a catalytic converter of claim 53, wherein theperovskite-type metal oxide deposited on the pre-coated support may bethe same or different from the bulk perovskite-type catalyst containedin the pre-coated support.
 55. The method of claim 54, wherein theperovskite-type metal oxide has a formulaLn_(0.5)Sr_(0.5)Mn_(0.98)Pd_(0.02)O₃, and the bulk perovskite-typecatalyst has a formula Ln₀ ₈Sr_(0.2)Mn₀ ₉O₃.
 56. The method of making acatalytic converter of claim 55, wherein the carrier is a mixture ofceria-zirconia and gamma alumina powders.
 57. The method of making acatalytic converter of claim 52 further comprising the steps of: (a)forming a homogeneous solution of a salt of a catalyst; (b) impregnatingthe solution onto washcoat of the support; and (c) calcining thepre-coated support impregnated with the solution for forming thecatalyst on the support.
 58. The method of making a catalytic converterof claim 57, wherein the solution contains single base or noble metalsor a binary mixture thereof.
 59. The method of making a catalyticconverter of claim 58, wherein the single base metal is selected from agroup consisting of metallic elements with atomic numbers 3-4, 11-15,19-32, 37-43, 48-52, 56-75, 80-83.
 60. The method of making a catalyticconverter of claim 58, wherein the noble metal is selected from a groupconsisting of elements with atomic numbers 44, 45, 46, 47, 76, 77, 78and
 79. 61. The method of making a catalytic converter of claim 58,wherein the binary mixture is a mixture of two single bases, a singlebase and a noble metal, or two noble metals.
 62. The method of making acatalytic converter of claim 58, wherein the catalyst solution has thecation ratio Sr₂Pd₀ ₁.
 63. The method of claim 43, wherein the supportis in the form of beads or pellets.
 64. The method of claim 63, whereinthe support is made of a carrier material.
 65. The method of claim 64,wherein the carrier material is selected from a group consisting ofaluminas, titania, silica, and the like.
 66. The method of claim 43,wherein the support structure is a honeycomb support.
 67. The method ofclaim 66, wherein the honeycomb support is a ceramic honeycomb support.68. The method of claim 66, wherein the honeycomb support is a metalhoneycomb support.
 69. A method of making a catalytic convertercomprising the steps of: (a) providing a carrier powder; (b) providing asupport; (c) depositing the carrier powder to the surface of the supportfor forming a washcoat on the surface of the surport; (d) forming ahomogeneous solution of a single phase mixed lanthanide salt of elementA collected from bastnasite and respective salts or oxides of elements Band M, wherein the ratio of A:B:M is the same as their ratio in theformula A_(1-x)B_(x)M; wherein A is a mixture of elements originally inthe form of a single phase mixed lanthanide collected from bastnasite; Bis a divalent or monovalent cation; M is at least one element selectedfrom the group consisting of elements of an atomic number of from 22 to30, 40 to 51, and 73 to 80; x is a number defined by 0≦x<0.5; (e)impregnating the solution onto the washcoat of the support, and (f)calcining the pre-coated support impregnated with the solution forforming a perovskite-type metal oxide on the pre-coated support.
 70. Themethod of claim 69, wherein the carrier powder is selected from a groupconsisting of titania, silica, gamma-alumina, alpha-alumina, ceria,zirconia, ceria-zirconia, ceria doped with rare-earths, alkaline earths,and transition metals.
 71. The method of claim 69, wherein the washcoatcomprises ceria-zirconia and gamma-alumina in ratios ranging from onepart ceria-zirconia to ten parts gamma-alumina (by weight) to washcoatscontaining only ceria-zirconia.